Covid-19: training dogs to sniff out the virus

What does a disease smell like? Humans might not have the answer, but if they could talk, dogs might be able to tell us. Able to sniff out a range of cancers and even malaria, canines' extraordinary noses are now being put to the test on Covid-19. Nicola Davis hears from Prof Dominique Grandjean about exactly how you train dogs to smell a virus, and how this detection technique could be used in managing the spread of Covid-19